[Rspamd] Sign Disposition-Notification Headers (#4020)

* [Rspamd] Sign Disposition-Notification Headers

Add more Headers to DKIM signing

* Update dkim_signing.conf

data/conf/rspamd/local.d/dkim_signing.conf

@@ -32,4 +32,4 @@ selector_prefix = "DKIM_SELECTORS";
 # forwards are arc signed, rejects are dkim signed
 sign_networks = "/etc/rspamd/custom/dovecot_trusted.map";
 use_domain_sign_networks = "header";
-sign_headers = "from:sender:reply-to:subject:date:message-id:to:cc:mime-version:content-type:content-transfer-encoding:resent-to:resent-cc:resent-from:resent-sender:resent-message-id:in-reply-to:references:list-id:list-help:list-owner:list-unsubscribe:list-subscribe:list-post:openpgp:autocrypt";
+sign_headers = "from:sender:reply-to:subject:date:message-id:to:cc:mime-version:content-type:content-transfer-encoding:content-language:resent-to:resent-cc:resent-from:resent-sender:resent-message-id:in-reply-to:references:list-id:list-help:list-owner:list-unsubscribe:list-subscribe:list-post:list-unsubscribe-post:disposition-notification-to:disposition-notification-options:original-recipient:openpgp:autocrypt";